Sound direction finder



March 25, 1947. s. M. GIANNINI SOUND DIRECTION FINDER Fi led March 22, 1943 s Sheets-Sheet 1 III/III INVENTOR. GABRIEL M. GIANNINI ATTORNEYS arch 25, 1947. s, M. GIANNINI 2,417,927

SOUND DIRECTION FINDER Filed March 22, 1943 5 Sheets-Sheet 2 NOISE LEVEL 2 NOISE LEVEL 0UTPUT 0F Q OUTPUT 0F MICRO. 0F MICRO INVENTOR. GABRIEL M. GIANNINI ATTORNEYS I arch 25, 1947.

G. M. GIANNINI 7,927

SOUND DIRECTION FINDER Filed March 22, 1943 5 Sheets-Sheet 3 179 ,me I f l v POWER .souRcE PiLoTAMPum fi """"2. 172 W lal I82 |73 LOCATOR AMPLlFIER 174 h 83 LOCATOR as MOTOR I23 I24 136 a m J85 MOTOR STOP '58 G} START WW4 INVENTOR.

GABRIEL M. GIANNINI ATTO R N EYS March 1947- G. M. GIANNINI ,927

SOUND EDIELCTICN IUDER F iled March 22. 1943 5 Sheets-Sheet 4 INVENTOR. GABRIEL M. summon ATTORNEYS Flas Patented Mar. 25, 1947 FlCE SOUND DIRECTION FINDER Gabriel M. Giannini, North Hollywood, Calif., as-

signor, by mesne assignments, to Automatic Electric Laboratories, Inc., a corporation of Delaware Application March 22, 1943, Serial No. 480,028

i! 1 The present invention relates to sound direction finders and more particularly to such finders of the electro-acoustic or microphone type.

It is an object of the present invention to provide a sound direction finder which is of compact and economical construction and arrangement and which is highly emcient in operation.

Another object of the invention is toprovide a sound direction finder comprising a plurality of movable microphones and utilizing an improved electric circuit arrangement for determining when the microphones are moved into substantial alignment with respect to a source of sound.

Another object of the invention is to provide a sound direction finder comprising an improved indicator arrangement for indicating when the direction of a source of sound has been established.

Another object of the invention is to provide a sound direction finder comprising an improved arrangement of a plurality of microphones. whereby the response of the finder is extremely sensitive.

A. further object of the invention is to provide a sound direction finder which is of improved construction and arrangement lending the finder particularly suitable for use aboard a ship or other craft.

A further object of the invention is to provide a sound direction finder which is of improved construction and arrangement lending the finder particularly suitable for use upon a submarine or other submersible device.

Further features of the invention pertain to the particular construction and arrangement of the mechanical and electrical elements of the sound direction finder, whereby the above-outlined and additional operating advantages are attained. i

I The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following specification taken in connection with the accompanying drawings, in which Figure 1 is a side elevational view, partly in section. of a sound direction finder embodying the present invention; Fig. 2 is a 1ongitudinal sectional view, taken in the direction of the arrows along the line 22 in Fig. 1 of the indicator incorporated in the sound direction finder; Fig. 3 is a plan sectional view, taken in the direction of the arrows along the line 3-3 in Fig. l, of the sound direction finder; Fig. 4 illustrates graphically the directional performance 15 Claims. (01. 177-386) characteristic of the pilot microphone incorporated in the sound direction finder; Fig. 5 illustrates graphically the directional performance characteristic of the locator microphone incorporated in the sound direction finder; Fig. 6 illustrates graphically the composite directional performance characteristic of the two microphones incorporated in the sound direction finder; Fig. 7 is a schematic diagram of the electric circuit incorporated in the sound direction finder; Fig. 8 is a side elevational View, partly in section, of a modified form of the sound direction finder; Fig. 9 is a front view of the instrument panel carried by the housing of the sound direction finder shown in Fig. 8; Fig. 10 is a plane sectional view of a further modified form of the sound direction finder; and Fig. 11 is a longitudinal sectional view of the sound direction finder shown in Fi 10.

Referring now more particularly to Figs. 1 to 3, inclusive, of the drawings, the sound direction finder I00 there shown comprisesan upstanding cylindrical tubular pedestal IOI,.a substantially spherical head I02 mounted on'the upper end of the pedestal "II, and an indicator I08 disposed remote from the head I02 and operatively con- ,i nected thereto by means of a flexible transmission cable I04 extending through the hollow pedestal I 0| The head I02 comprises a disk-shaped collar I05 suitably mounted on the upper end of the tubular pedestal IN, a lower semispherical shell I08 welded to the collar I05 as indicated at I01, an upper semispherical shell :08 and four radially spaced-apart straps I09 extending between and securing together the lower and upper shells I08 and I08. The straps I08 are secured to the lower and upper shellsIIIIi and I08 by removable bolts I I0 extending through aligned openings provided in the adjacent walls of the associated shells and the ends of the straps I00, the ends of the bolts IIO being threaded to receive cooperating nuts III, whereby the upper and lower shells I06 and I08 are retained together in spacedapart relation. A disk-shaped top plate II! is suitably secured in the open end of the upper shell I08; and a disk-shaped bottom plate H3 is suitably secured in the open end of the lower shell I00.

Centrally disposed in the head I02 is a rotatable shaft H4 which extends through a centrally located opening provided in the bottom plate I I3, the upper end of the shaft I I4 being located by a suitable guide bearing II5 carried by the lower surface of the top plate I I2 and the lower end of the shaft H4v being located by a suitable guide bearing II6 carried by the upper surface of the collar I05. Finally the shaft II4 is mounted for rotation upon thrust bearing structure including an upper thrust ring I I1 secured to the shaft II4 by a pin II8 and a lower thrust ring II9 secured to the upper surface of the bottom plate I I3 and surrounding the centrally disposed opening formed therein, suitable balls I being arranged in bearing channels formed in the upper and lower thrust rings I I1 and I I9. At this point it is noted that the extreme lower end of the shaft H4 is rigidly connected to one end of the flexible transmission cable I04 extending to the indicator I03. Also the shaft II4 carries a gear I2I which cooperates with a pinion I22 secured to the shaft of a suitableelectrical motor I23, the frame of the motor I23 being suitably secured to the lower surface of the bottom plate II3; whereby the shaft II4 may be rotated by I theeelectric motor I23 in an obvious manner.

Also the shaft II4 carries a substantially diskshaped platform I24 which is disposed between the top plate I I2 and the bottom plate I I3. whereby the platform I24 may be rotated with the shaft II4 between the plates mentioned.

The upper surface of the platform I24 carries a pilot microphone I25 and a locator microphone I26 arranged in nested relation, as clearly indicated in Fig. 3. Preferably, the pilot microphone I25 is of the ordinary directional type and of the construction disclosed in the copending application of Gabriel M. Giannini, Serial No. 419,165, flled November 14, 1941, now patent No. 2,341,539, granted February 15, 1944; while the locator microphone I28 is of the balanced directional type and of the construction disclosed in the copending application of Gabriel M. Giannini, Serial No. 419,166, flied November 14, 1941.

. More particularly. the pilot microphone I 25 comprises a single insulating structure I21 through which communicating sound passages are formed; while the locator microphone I26 comprises two spaced-apart insulating structures I28 through which communicating sound passages are formed; the structure I21 being disposed intermediate the structures I28, as previously noted. Closure structure is secured to the upper surface of the platform I24 which extends between the platform I24 and the lower rim of the upper shell I08; which closure structure comprises nested inner and outer cylindrical rings I29 and I30. The lower end of the inner ring I29 is flanged inwardly and directly secured to the upper surface of the platform I24 as indicated.

at I3I; the lower end of the outer ring I30 is flanged outwardly away from the periphery of the platform I24 as indicated at I32; while the upper ends of the inner and outer rings I29 and I30 are disposed within the lower rim of the upper shell I08. Also it is noted that suitable re istering openings are provided in the inner and outer rings I29 and I80 which communicate with the sound passages formed in the structures I21 and I28 which in turn communicate with the pilot microphone I25 and the locator microphonerotation of the platform I24 and the ring I29 and I30 secured thereto with respect to the transparent ring I33 and the lower rim of the upper shell I08, and seals the interior of the head I 02 against damage due to inclement weather.

Further, the lower surface of the platform I24 carries an angular bracket I34 upon which a lamp I35 and an audible alarm or buzzer I36 are mounted, the lamp I35 being disposed within, and a short distance from, the transparent ring I33, whereby the lamp I35, when illuminated, Is visible as a bright spot through the adjacent section of the transparent ring I33. Finally the shaft II4 carries commutating structure I31 which cooperates with wipers I38 carried by an insulator I39 secured to the lower surface of the top plate I I2, whereby the relatively rotatable and stationary electrical elements of the sound direction flnder I00 may be electrically connected together.

As best shown in Figs. 1 and 2 of the drawings, the indicator I03 comprises a substantially cupshaped shell I in which a centrally located shaft I5I is suitably iournaledfor rotation, the shaft I5I being rigidly connected to the flexible transmission cable I04. A transparent ring I52 is secured in the open end of the shell I50 and carries a disk I53 having an opening therein through which the outer end of the shaft I5I projects. The outer end of the shaft I5I carries a pointer I54 which cooperates with suitable indicia I55 disposed about the outer surface of the transparent ring I52. Also the shaft I5I carries a disk I56 disposed below the transparent ring I52, the disk I56 carrying an angular bracket I51 which supports a lamp I58 and an audible alarm or buzzer I59. Also the disk I58 has a radially disposed slot I56a formed therein adjacent the periphery thereof which provides for the passage of light from the lamp I58 through the transparent ring I52, the lamp I59 being disposed'inwardly and in direct alignment with the slot I56a formed in the disk I56 and the transparent ring I52. Finally the shaft I5I carries commutating structure I60 which cooperates with wiper IGI carried by an insulator I62 secured to the inner surface of the bottom wall of the shell I50, where- 'by the relatively rotatable and stationary electriany suitable form, a locator amplifier "I of the vacuum tube type and of any suitable form, a pilot relay I12 any suitable type provided with a pair of make contacts I13, a locator relay I14 of any suitable type provided with a pair of break contacts I15, a power panel I16 provided with a start key I11 and a motor stop key I18, a loud speaker I19 of any suitable type, a receiver set I of any suitable type and a source of power supply indicated. More particularly, the pilot amplifier I10 comprises a power input circuit adapted, to be closed by the start key I11 across the line conductors of the power source, a signal input circuit connected to the pilot microphone I25, a signal relay output circuit connected to the pilot relay I12, a signal speaker output circuit connected to the loud speaker I19, a signal receiver output circuit connected to the receiver set I80, first gain control equipment for governing the gain of the signal relay output circuit and controlled by the dial I8I, and second gain control equipment for governing the gain of the signal speaker and signal receiver output circuits and controlled by the dial I82. Similarly, the locator amplifier. I'll comprises a. power input circuit adapted to be closed by the-start key I11 across the line conductors of the power source, a signal input circuit connected to the locator microphone I26, a signal relay output circuit connected to the locator relay I14, and gain control equipment for governing the gain of the signal relay output circuit and controlled by the dial I83. The motor I23 includes an operating circuit which is adapted to be closed by the start key I11 across the line conductors of the power source through the-motor stop key I18, the motor I23, the motor stop key I18 and the start key I11 being arranged in series circuit relation. Finally the lamps I35 and I58 and the buzzers I36 and I59 are connected in multiple across the conductors I84 and I85; which conductors may be bridged across the line conductors of the power source when the start key I11 is operated, the locator relay I14 is restored and the pilot relay I 12 is operated, whereby the lamps I35 and I58 are illuminated and the buzzers. I35 and I59 are operated to produce an audible alarm. a

Considering now the directional performance characteristics of the pilot microphone I25 and the locator microphone I26, reference is had to the graphic illustrations appearing in Figs. 4 to 6, inclusive", of the drawings. Referring particularly to Fig. 4, it is noted that the pilot microphone I25 has a maximum output when it is directed toward the left in the direction of the source of sound along the horizontal line I90 indicated, and a minimumoutput when it is directed toward the right away from the direction of the source of sound along the horizontal line I 90; wherey the output characteristic of the pilot microphone I25 conforms to the single petal pattern outlined by the performance curve I9I.

Assuming a circular noise level curve I92, it will be noted that the performance curve I9I of the pilot microphone I25 projects beyond the noise level curve I92 only between the points a and b. Referring particularly to Fig. 5, it is noted that the locator microphone I26 has a maximum output when it is directed toward the left at an angle with respect to the direction of the source of sound either along the inclined line I93 indicated or the inclined line I94 indicated, the inclined line I98 being disposed above the horizontal line I60 at an angle of approximately 30 and the inclined line I94 being disposed below the horizontal line ,I90 at an angle of approximately 30; the locator microphone I25 has a minimum output -when it is directed toward the left in the direction of the source of sound along the horizontal line I90, and. six points of peak and six points of valley output interposed therebetween; whereby the output characteristic of the locator microphone I26 conforms to the six petal pattern outlined by the performance curve I95. Again assuming the circular noise level curve I92, it will be noted that the performance curve I95 of the locator microphone I26 dips below the noise level curve six times between the points c-d, e-f, g--h, i-k, m-n and p-q. Now referring particularly to Fig. 6 comprising a composite illustration of the performance curve I9I of the pilot microphone I25, the .performance curve I95 of.

the locator microphone I26 and the noise level curve I92, it will be understood that simultaneously the performance curve I9I projects beyond the noise level curve I92 and the performance curve I95 dips below the noise level curve I92 only between the acute angle defined by the inclined lines I96 and I91 directed toward the center of the circular noise level curve I92 and respectively disposed above and below the horizontal line I90, The utilization of the joint condition mentioned of the pilot microphone I and the locator microphone I26, when the head I02 of the sound direction finder I00 is disposed in the acute angle defined etween the lines I96 and I81, is explained more fully hereinafter.

Now considering the mode of operation of the sound direction finder I00 both with respect to the mechanical and electricaifeatures of the operation thereof, it is noted that the pedestal IN is mounted upon a suitable support In a substantially vertical direction, whereby the platform I 24 is rotatablein a substantially horizontal plane. At this time operation of the sound direction finder I00 is initiated by closing the start key I11, whereby the previously traced circuit, including the motor stop key I18, is completed for operating the motor I23, which operating circuit is maintained..- assuming that the start key I11 is of the locking type. Also when the start key I11 is closed the previously traced power circuits for the pilot amplifier I10 and the locator amplifier I are completed, rendering the amplifiers mentioned operative. Upon operating, the motor I23 rotates the pinion I22 and consequently the shaft II4 through the gear I2I in either direction desired. The shaft H4 is mounted for rotation upon the thrust bearing arrangement, including the thrust rings H1 and H9 and the balls I20, whereby the platform I24 and the commutator structure I31 are rotated with the shaft II4. As the platform I24 is thus rotated the pilot microphone I25 and the locator microphone I26 are rotated, whereby the microphones mentioned are first moved toward and then away from the direction of a source of sound.

Now assuming that there is a source of sound existent, the direction of which is to be located by the sound direction finder I00, the output characteristics of the pilot microphone I25 and the locator microphone I26 conform to the performance curves I9I and I illustrated in Figs. 4 to 6, inclusive, of the drawings, as previously explained. More particularly, the pilot microphone I25 operates to impress a signal upon the associated signal input circuit; whereby the signal mentioned is amplified and impressed by the pilot amplifier I10 upon the associated signal relay output circuit, signal speaker output circuit and signal receiver output circuit. The first gain control equipment of the pilot amplifier I10-is adjusted by the dial I8I, whereby the output current supply to the signal relay output circuit conforms to the performance curve I9I illustrated in Fig. 4; which current is of sufficient magnitude to effect operation of the marginal pilot relay I12 only when the performance curve I9I projects beyond the noise level curve I92. Accordingly, it will be understood that the pilot relay I12 is operated only during the arc of rotation of the platform I24 disposed between the points a and b, as indicated in Fig. 4. Also the second gain control equipment of the pilot amplifier I10 is adjusted by the dial I82, whereby the output current supply to the signal speaker output circuit and to the signal receiver output circuit conforms to the performance curve I9I illustrated in Fig. 4; which current is of sufficient magnitude to: effect appreciable operation of the loud speakezi I19 and the receiver set I80 only when the performance curve i9I projects beyond the noiselevel curve I92. Accordingly, it will be understood that the loud speaker I19 and the receiver set I80 are operatedappreciably only during the arc of rotation of the platform I24 disposed between the points a and b, as indicated in Fig. 4, More particularly, the locator microphone I26 operates to impress a signal upon the associated signal input circuit; whereby the signal mentioned is amplified and impressed by the locator amplifier I1I upon the associated signal relay output circuit. The gain control equipment of the locator amplifier "I is adiusted by the dial I83, whereby the output current supply to the signal relay output circuit conforms to the performance curve I95 illustrated in Fig. 5; which current is of insufficient magnitude to eflect the restoration of the marginal locator relay I14 only when the performance curve I95 dips below the noise level curve I92. Accordingly, it will be understood that the locatorrelay I14 is restored only during the arcs of rotationoi the platform I24 disposed between the points c-d, ef,- 9-11., i-k, m-n and as indicated in Fig. 5. Thus it will be understood that simultaneously the pilot relay I12 is operated and the locator relay I14 is restored only during the narrow arc of rotation -of the platform I24 defined'between'the acute angle formed by the inclined lines I06 and I91, as indicated in Fig. 6. 7

When both the pilot relay I12 is operated and the locator relay I14 is restored, the angular position of the platform I24 is disposed within the acute angle formed'by the inclined lines I96 and I9 1, as explained in conjunction with Fig. 6; whereby the sound direction finder I00 has located the direction of the source of sound. At this time, when the pilot relay I12 is operated and the locator relay I 14 is restored, the previously mentioned multiple circuits for illuminating the lamps I35 and I58 and for operating the buzzers I36 and I59 are completed. When the buzzers I36 and I59 are thus operated the motor stop key I18 is operated, thereby to interrupt the previously'traced operating circuit for the motor I23; which operating circuit is retained interrupted, assuming that the motor stop key I18 is of the locking type. When the operating circuit for the motor I23 is thus interrupted, furtheroperation thereof is arrested and, consequently, further rotation of the shaft H4 and the platform I24 is arrested. At this time the pilot microphone I25 and the locator microphone I26 are directed toward the source of sound, as previously explained.

At this time the illuminated lamp I disposed below the transparent ring I33 is visible as a bright'spot therebelow, whereby the angular position of the'platform I24 and consequently the therewith, whereby the shaft I5I of the indicator I03 is correspondingly rotated. The pointer I54 carried by the end of the shaft I6I and cooperating with the indicia I55 borne by the transparent ring I52 is so adjusted that at any time the angular position of the platform I24 may be read directly from the indicator I03 due to the cool eration between the pointer I54 and the indicia I55 borne by the transparent ring I52. Accordingly, at this time, the illuminated lamp I58 disposed below the disk I56 and the transparent ring I52 projects a beam of light through the slot I 56a formed adjacent the periphery of the disk I56 and appears as a bright spot below the transparent ring I52, whereby the angular position of the platform I 24 and consequently the direction of the source of sound are established; whereby the angular direction of the source of sound may be interpreted directly from the indicator I03. At this point it is noted that the indicia I55 borne by the transparent ring I52 may be calibrated in ordinary compass values. Also the operation of the buzzer I59 directs attention to the fact that the platform I24 occupies its angularly adjusted position in the direction of the source of sound.

In order to arrest operation of the sound direction finder I00, it is only necessary to open the start key I11, whereby the previously traced multiple circuits for illuminating the lamps I36 and I58 and for operating the buzzers I36 and I59 are interrupted. Also when the start key I11 is opened the power input circuits of the pilot amplifier I10 and the locator amplifier "I are interrupted in order to arrest operation thereof; When operation of the pilot amplifier I10 is thus arrested the pilot relay I12 restores and further operation of the loud speaker I19 and the receiver set I30 is arrested, and when operation of the locator amplifier "I is thus arrested the-locator relay I14 is retained in its restored position. At

this time the operation of the sound direction finder I00 is completely arrested and all of the electrical elements thereof are deenergized. In connection with the operation of the sound direction finder I00 it is noted that the lamps I35 and I58 and the buzzers I36 and I59 are respectively illuminated and operated periodically as the platform I24 continues to rotate. Thus it will be understood that the rotation of the platform I24 may be arrested at any convenient time when the lamps I35 and I58 are illuminated and the buzzers I36 and I59 are operated by opening the motor stop key I18, in the manner previously explained. Finally, in connection with the release of the sound direction finder I00, it is pointed out that after the start key I11 is opened the motor stop key I18 is reclosed, thereby again conditioning the sound direction finder I00 for reoperation merely by again closing the start key I11. Further, in connection with the operation of the sound direction finder I00, it is pointed out that when the platform I24 is rotated to establish the direction of the source of sound, the loud speaker I13 and the receiver set I also produce a maximum output which may be detected audibly. Thus it will be understood that the operation of the sound direction finder I00 to locate the angular direction of the source of sound is indicated not only at the head I02 by the illumination of the lamp I36 andthe operation of the buzzer I36, but it is also indicated by the operation of the loud speaker I19 and the reoeiver set I80 as well as by the indicator I03 disposed at the remote point. More particularly, in the indicator I03, the illumination of the lamp I58 and the operation of the buzzer I59 both indicate the condition mentioned.

Referring now more particularly to Figs. 8 and 9 of the drawings, the modified form of the sound direction finder 200 there shown is adapted to be supported by the deck of a ship or other craft, whereby the upper portion of the sound direction finder 200 projects above the deck 20I and the lower portion of the sound direction finder 200 projects below the deck 201 into a suitable compartment provided in the ship. More particularly, the sound direction finder 200 comprises a cylindrical tubular member 202 which projects through a supporting bracket 203 mounted on the upper surface of the deck 20l; the supporting bracket 203 comprising a tubular body 204 carrying an annular ring 205, and upstandlng'triangular braces 206 extending between the tubular body 204 and the annular ring 205. The

supportin -bracket 203 is firmly secured in place upon the deck 20! by an arrangement comprising a clamping ring 201, a collar 208 formed of wood or the like and disposed between the upper surface of the deck 2M and the annular ring 205, a collar 209 formed of woodor the like and disposed between the lower surface of the deck 20! and the clamping ring 201, and a number of bolts 210; the bolts 2l0 extending through aligned openings provided in the annular ring 205, the clamping ring 201, the deck 20I and the collars 208 and 209 and receiving cooperating nuts 21! on the threaded ends thereof. Disposed between the tubular member 202 and the tubular body 204 are two connections 2l2 and 213 respectively disposed adjacent the upper and lower ends of the tubular body 204; which connections 2l2 and 213 permit relative turning movement between the tubular member 202 and the tubular body 204.

More particularly, the connection 2l2 combody 204. Further the upperend of the sleeve 2 comprises a bearing surface projecting into an annular recess 216a formed in the under-surface of the skirt 2l5, thereby to support the skirt 2l6 and the tubular member 202 and further to seal the parts mentioned. Finally a gasket 211 disposed in an annular recess formed 10 the sleeve 218. Further the lower end oi-the sleeve 2| 8 comprises a bearing surface projecting into an annular recess 220a formed in the upper surface of the skirt 220, thereby to prevent lateral movement of the skirt 220 and consequently the tubular member 202. Finally a gasket 22! disposed in an annular recess formed in the lower end of the sleeve 218 is disposed between the lower end lot the sleeve M8, the adjacent surface oi the, tubular member 202 and the adjacent upper surface of the-skirt 220 in order to seal the parts mentioned. Thus it will be understood that the connection 2l3 not only guides the rotatable support of the tubular member E02 upon the supporting bracket 203 but it also provides a resilient mounting or cushion therebetween and further effectively seals the connection between the tubular member 202 and the tubular body 204.

The upper end of the tubular member 202 terminates in a head 222 which comprises an upwardly directed cup-shaped shell 223 directly secured to the upper end of the tubular'member 223 by an arrangement comprising a cylindrical reticulated screen 225. More particularly, the lower end of the reticulated screen 225 is suitably embedded in an annular recess formed in the upwardly directed open rim'of the shell 223; and the upper end of the reticulated screen 225 is suitably embedded in an annular recess formed in the downwardly directed open rim of the cap 224. Rotatably mounted within the upper end of the tubular member 202 andthe shell 223 is a stub shaft 226, which is supported by a bearing arrangement comprising a, cylindrical sleeve 22'! disposed within the upper end of the tubular member 202. More particularly, the upper end of the sleeve 221 is secured to the adjacent inner surface of the tubular member'202 adjacent the upper end thereof by an interposed mounting ring 228 formed of rubber or the like; and the lower end of the sleeve 221 carries a fixture 229, which is secured to the adjacent inner surface of the tubular member 202 by an annular mounting ring 230 formed of rubber or the like. The

in the upper end of the sleeve 2 is disposed between the upper end of the sleeve 214, the adjacent surface of the tubular member 202 and the adjacent undersurface of the skirt 2IB in order further to seal the parts mentioned. Thus it will be understod that the connection 2l2 not only rotatably supports the tubular member 202 upon the supporting bracket 203 but it also provides a resilient mounting or cushion therebetween and further efiectively seals the connection between the tubular member .202 and the tubular body 204. More particularly, the connection 2l3 comprises asleeve 210 surrounding the tubular member202 and secured to the inner surface of the tubular body 204 by an interposed mounting ring 2I 9 formed of rubber or the like. Also the connection 2| 3 comprises an upwardly directed skirt 220 rigidly secured to the tubular member 202 and covering the lower end of the tubular body 204, the mounting ring 2|! and upper end of the sleeve 221 carries a step bearing 23i which supports the stub shaft 226; and the fixture 229 carries a guide bearing 232 adjacent the lower end of the sleeve 221, which prevents lateral movement of the stub shaft 226. Finally the upper end of the sleeve 221 carries an annular cap 233 having an opening in the end thereof through which the stub shaft 226 extends, a gasket 234 being arranged mutually between the cap 233,, the step bearing 23l, the upper end vides the stub shaft 226 with a resilient mounting with respect to the tubular member 202.

A rotatable transmitter support 235 is arranged within the head 222 in alignment with respect to the reticulated screen 225, and is rigidly secured to a fixture 233. The fixture 230 .ing ring 238 formed of rubber or the like;

portion 231 surrounding theend of the stub shaft 226 and resiliently connected thereto by a mount- Accordingly, the transmitter support 235 is resiliently mounted on the upper end of the stub shaft 226 by the mounting ring 238 for rotation with the stub shaft 226 within the head 222 and in alignment with respect to the reticulated screen 225. The transmitter support 235 carries a suitable pilot microphone and a locator microphone, not shown, which are mounted within the structure thereof and take any suitable forms, such, for example, as the arrangement of the microphones disclosed in conjunction with the sound direction finder I00.

As previously noted, the lower end of the tubuiar member 202 projects through the deck 20! and terminates within a compartment formed in the ship; and the lower end of the tubular memher 202 rotatably supports an instrument housing 239. More particularly, a tubular sleeve 240 is rigidly secured to'the lower end of thetubular member 202 and a tubular sleeve 2 is rigidly secured to the upper surface of the housing 239, the sleeve 2 surrounding the sleeve 240 and being rotatably supported thereby, whereby the sleeve 240 constitutes a step bearing supporting the sleeve 2 and consequently the housing 239 secured to the sleeve 24!. Also the lower end of the tubular member 202 carries a downwardly directed skirt 242 covering the sleeves 240 and 2 and terminating immediately adjacent the upper surface of the housing 239. An arrangement including a gasket 243, formed of rubber or the like, disposed in an annular recess provided in the upper end of the sleeve 24I and positioned mutually between the sleeve 2, the sleeve 240 and the undersurface of the skirt 242, is provided for sealing the relative rot'atable sleeves 240 and 2. Also a gasket 244 disposed in an annular'recess formed in the lower end of the sleeve 24I and disposed between the adjacent surfaces of the sleeves 240 and 24l is provided in order further to seal the relatively rotatable sleeves mentioned.

The hous ng 239 comprises a hollow box-like structure provided with a removable front wall or instrument panel 245 and two handles 246 secured to the opposite side walls thereof, the handles 245 accommodating ready rotation of the housing 239 with respect to th skirt 242 carried by the tubular member 202. Within the housing 239 certa n mechanical and electrical equipment are provided. More particularly, an electrical motor 241 and an associated transmission mechanism 249 are provided in the housing 239; the transmission mechan sm 248 rotatably supports a drive shaft 249, the upper end of which is secured to the lower end of the stub shaft 226 by a fixture 250 disposed within the tubular member 202, Also the section of the drive shaft 249 extending between the interior of the housing 239 and the interior of the tubular member 202 is supported by a bearing 25I carried by the upper wall of the housing 239. Also a panel 252 is arranged within the housing 239 and resiliently supported by the side wall thereof by an arrangement comprising a number of resilient blocks 253 formed of rubber or the like; the panel 252 carrying certain of the electrical equipment including a pilot amplifier 254 and a, locator amplifier 255. The side wall of the housing 239 carries a start key 256; and the front wall 245 carries other of the electrical equipment including a motorstop key 251, an indicator 256, a meter 259 and a lamp 260. The indicator 258 is operatively associated with the transmission mechanism 246- and comprises a pointer 26! and an associated scale 262, whereby the relative angular position of the operating shaft 249 with respect to the housing 239 may be readily interpreted. In the sound direction finder 200 the electrical circuit arrangement is substantially identical to that provided in the sound direction finder I00 and illustrated in Fig. '7 of the drawings. More particularly, in this case, the pilot amplifier 254 comprises a signal relay output circuit connected to a pilot relay, not shown, a signal meter output circuit connected to the meter 259, first gain control equipment for governing the gain of the signal relay output circuit and controlled by a dial 263 carried by the front wall 245, and second gain control equipment for governing the gain of the signal meter output circuit and controlled by a dial 264 carried by the front wall 245; and the locator amplifier 255 comprises a signal relay output circuit connected to a locator relay, not shown, and gain control equipment for governing the gain of the signal relay output circuit and controlled by a dial 295 carried by the front wall 245. Finally the lamp 250 is provided with a control circuit governed by the pilot relay and the locator relay, not shown.

In view of the foregoing description of the construction and arrangement of the sound direction fin'der 200, it will be understood that after it is mounted upon the deck 20l the tubular member 202 thereof is rotated to a position of proper orientation and thereafter no further rotation of the tubular member 202 during normal operation of the sound direction finder 200 is contemplated. Finally it is pointed out that the lower end of the skirt 242 carries reference indicia 266 which cooperates with suitable reference indicia, not shown, carried by the top wall of the housing 239, whereby the relative anglilar position of the housing 239 with respect to the skirt 242 and the tubular member 202 may be readily interpreted.

In order to initiate operation of the sound direction finder 200, the start key 258 is operated, whereby operation of the motor 241 is initiated. The motor 241 causes rotation of the operating shaft 249 through the transmission mechanism 248, whereby the stub shaft 226 and the transmitter support 235 are rotated, the transmitter support 235 being rotated below the reticulated screen 225, causing the supported pilot and locator microphones to sweep a horizontal field, in an obvious manner. The transmission mechanism 248 causes operation of the indicator 253, whereby the relative position of theoperating shaft 249 with reference to the housing 239 and consequently the relative angular position of the microphone support 235 may be readily interpreted by the cooperation of the pointer 26! and the associated scale 262. The pilot microphone and the locator microphone carried by the microphone support 235 determine the direction of the source of sound in the manner described in conjunction with the operation of the sound direction finder I00, whereby the associated pilot amplifier 254 and the locator amplifier 255 are controlled, causing the lamp 200 to be illuminated when the approximate angle of the direction of the source of sound is located. At this time the motor stop key 251 may be operated.

Thereafter the position of the housing 239 with respect to the skirt 242 may be adjusted by means of the handles 246, causing further rotation of the operating shaft,249 and consequently the microphone support 235. When the housing 239 is rotated with respect to the skirt 242 by the handles 246 the operating shaft 249 and the transmission mechanism 248 are rotated therewith, whereby there is no further adjustment of the relative angular position between the operating shaft249 and the transmission mechanism 240 and consequently no further operation of the indicator 258. At this time the angular position the housing 239 with respect to the skirt 242 no consequently further adjustment of the miwrophone support 235 may be eifected by the "handles 2%, whereby the pilot microphone carried by the microphone support 235 governs the associated pilot amplifier 254 in order to cause the ,lmeter 250 to produce a maximum reading. At

this time the precise angle of the direction of the gsdurce of sound is located and may be readily lf dctermlned by a combination of readings taken i from the indicator 258 and the indicia 266. In

'7 other words, the relative angular position of the operating shaft 249 with respect to the housing l 238 is determined by the indicator 258; and the tiibular member 202. Having determined the angular position of the microphone support 235 with respect to the tubular member 202, and having previously orientated the angular position of the tubular member 202 with respect to thefcenter line of the ship, the exact compass *position of the direction of the source of sound may be readily determined. r e Referring now more particularly to Figs. 10 ,8 and 11 of the drawings, the further modified form f'the sound direction finder 300 there shown is adapted to be supported by the periscope of a submarine or other submersible craft or by a iiiiving bell or the like. The sound direction Kinder 300 comprises a base 301 which is adapted wto be directly secured to the periscope or other rotatable part and a substantially bell-shaped casing 302 hermetically sealed to the base 30L ,the casing 302 including a'remcvable dome 303 f-Lihe'rmetically sealed thereto. The interior of the "ca sing 302 is hollow and carries a substantially centrally disposed supporting ring 304 upon which is mounted an upstanding annular frame 305, the frame 305 being mounted upon the supporting ring 304 by means of a mounting ring 306 formed of rubber or the like, whereby the frame 305 is resiliently supported by the supporting ring 304. One end of the frame 305 is hermetically sealed by an arrangement comprising a substantially semi- -spherical and inwardly directed diaphragm 301, a substantially semispherical and inwardly directed reticulated screen 308, an intervening spacing ring 309, and a clamping ring 3|0. the reticulated screen 308 directly engaging the adjacent end of the frame 305, the spacing ring 309 being disposed between the peripheral portions of the reticulated screen 308 and the diaphragm 301 and the clamping ring 3|0 directly engaging the adjacent peripheral portion'of the diaphragm 301. The elements named are retained in assembled relation by screws or the like, not shown, whereby the adjacent end mentioned of the frame 305 lib , 14 is hermetically sealed. Similarly, the other end of the frame 305 is hermetically sealed by an arrangement comprising a substantially semispherical and inwardly directed diaphragm 3| l, a substantially semispherical and inwardly directed reticulated screen 3|2, an intervening spacing ring 3|3, and a clamping ring 3|4, the reticulated screen 3|2 directly engaging the adjacent end of the frame 305, the spacing ring 3|3 being disposed between the peripheral portions of the reticulated screen 3|2 and the diaphragm 3H and the clamping ring 3l4 directly engaging the adjacent peripheral portion of the diaphragm 3. The elements named are retained in assembled relation by screws or the like, not shown, whereby the adjacent end mentioned of the frame 305 is hermetically sealed.

Accordingly, the two inwardly directed reticulated screens 308 and 3|2 are respectively spaced with respect to the associated diaphragms 301 and 3| to protect the diaphragms mentioned and are disposed substantially in contact with each other adjacent the centers thereof at the approximate center of the frame 305. Also a substantially centrally disposed conduit 3|5 is arranged within a recess 30|a formed in the base 30l and projects through an opening provided in the top wall of the base 301, the upper end of the conduit 3|5 being flared outwardly to provide a substantially cone-shaped throat 3l6 secured in a, cooperating conical opening provided in the bottom of the frame 305, whereby the interior of the compartment defined between the frame 305 and the cooperating diaphragms 301 and 3||-s communicates through the conduit 3|5 with the exterior. Also a breather tube 3" is arranged within the conduit 3|5 and extends toward the top of the compartment mentioned defined between the frame 305 and the diaphragms 301 and 3| I, the breather tube 3| 1 having an oifset central portion disposed out of contact with respect to the reticulated screens 308 and 3|2, whereby the interior of the compartment mentioned may be vented through the breather tube 3l1. The breather tube 3|1 is suitably supported in the throat 3H5 of the conduit M5 by an associated plug 3|8, the breather tube 3|1 extending through an opening formed in the plug 3I8 and the plug 3| 8 having other openings therein directly connecting the interior of the compartment formed between the frame 305 and the diaphragms 301 and 3H and the interior of the throat 316 of the conduit 3l5.

The diaphragm 301 forms a part of a first microphone which also includes a substantially C-shaped field structure 3|9 carrying a winding 01. coil 320, the field structure 3|3 being suitably secured to the clamping ring 3|0 by a number of blocks or wedges 32| illustrated. The diaphragm 301 is formed of magnetic material while the field structure 3l9 comprises a permanent magnet arranged in spaced relation with respect thereto, whereby a magnetic field is normally set up between the north and south poles of the permanent magnet 3|9 which includes the adjacent section of the diaphragm 301. Also the blocks 32| disposed between the permanent magnet 3|3 and the clamping ring 3|0 are formed of nonmagnetic material, thereby to prevent flux leakage between the top and bottom portions of the permanent magnet 319 and the adjacent peripheral portion of the diaphragm 301. The first microphone, comprising the permanent magnet 3|9 and the coil 320, is embedded in a molded block 322 formed of rubber or the like and filling a portion of the interior of the casing 302 disposed between the clamping ring 3i0 and the adjacent inner side wall of the casing 302. The block 322 has a" number of openings 323 formed therein out of contact with the permanent magnet 3|9 and the coil 320 and communicating between a chamber 324 defined between the block 822 and the adjacent surface of the diaphragm 301, the openings 323 also communicating through openings 325 formed in the casing 302. Accordingly, the chamber 324 defined between the diaphragm 301 and the block 322 communicates with the exterior through the openings 323 formed in the block 322 and the openings 325 formed in the casing 302.

Similarly, the diaphragm 3| forms a part of a second microphone which also includes a substantially C-shaped field structure 326 carrying a winding or coil 321, the field structure 326 being suitably secured to the clamping ring 3 by a number of blocks or wedges 328 illustrated. The diaphragm all is formed of magnetic material while the field structure 326 comprises a permanent magnet arranged in spaced relation with respect thereto, whereby a magnetic field is normally set up between the north and south poles of the permanent magnet 326 which includes the adjacent section of the diaphragm 3| I. Also the blocks 320 disposed between the permanent magnet 326 and the clamping ring 3M are formed of the nonmagnetic material, thereby to prevent flux leakage between the top and bottom portions of the permanent magnet 320 and the adjacent peripheral portion of the diaphragm 3. The second microphone, comprising the permanent magnet 326 and the coil 321, is arranged within an air filled cavity 320 formed in the casing 302 adjacent the diaphragm 3| Finally a terminal block 330 is provided which is supported in a recess formed in the frame 305; which terminal block terminates the coils 320 and 321. Finally it is noted that the terminal block 330 may be electrically connected through the compartment formed between the frame 305 and the diaphragms 301 and 3, the plug 3|3 and the conduit M6 to the exterior. Preferably, the two microphones are wired in opposition to each other, whereby the sound direction finder 300 is of the balance type.

chamber 324 defined between the diaphragm 301 and the block 322 through the openings 323 is drained therefrom after the sound direction finder 300 is positioned in the associated atmosphere; and that such water has no deleterious effect upon the second microphone due to the water impervious nature of the material of which the block 322 embedding the elements of the second microphone is formed. At this time the chamber 324 formed adjacent the diaphragm 301 and the block 322 is directly connected via the openings 323 to the atmosphere; while the cavity 329 disposed adjacent the diaphragm 3|| of the second microphone is shielded by the side wall of the casing 302. Hence, the first microphone will produce a greater output than the second microphone, assuming that the same intensity of sound is reaching the diametrically disposed surfaces of the casing 302, as will be readily appreciated. At

i6 this time the base 3M and consequently the easing 302 are rotated until a maximum output is obtained from the two balanced connected microphones. At this time the first microphone comprising the permanent magnet 3|9 and the coil 320 is directed toward the source of sound, whereby the associated apparatus, through which the sound direction finder 300 is revolved, is operative to indicate the direction of the source of sound in ordinary compass values, in the manner previously explained. The construction of the sound direction finder illustrated in Figs. 10 and 11 is claimed in a copending divisional application Serial No. 621,062. filed October 8, 1945.

While the preferred embodiments of the invention have been disclosed, it will be understood that various modifications may be made therein which are within the true spirit and scope of the invention.

What is claimed is:

1. A sound direction finder comprising a member mounted for rotation, two microphones having sound openings facing in the same direction supported by said member, the individual outputs of said microphones varying in accordance with established patterns in response to rotation of said member with respect to-a direction line extending between said member and a source of sound, said microphones being so constructed and arranged that they respectively produce maximum and minimum points of output in their individual output patterns only when said member occupies a substantially fixed angular position with respect to said direction line, whereby the production of maximum and minimum points of output in said individual output patterns for producing a signal.

2. A sound direction finder comprising a member mounted for movement, a first microphone of the directional type and a second microphone of the balanced directional type supported by said member, said microphones having sound openings therefor facing in the same direction for the reception of sound, the output of said first microphone varying in response to movement of said member and being a'maximum when said sound openings are substantially aligned with respect to a direction line extending between said member and a source of sound, the output of said second microphone varying in response to movement of said member and being a minimum when said sound openings are substantially aligned with respect to said direction line, whereby the position or direction of said source of sound with respect to said member is established when the outputs of said first and second microphones are respectively maximum and minimum, and means responsive jointly to maximum and minimum outputs of said first and second microphones respectively for producing a signal.

3. A sound direction finder comprising a member mounted for rotation, a first microphone of the'directional type and a second microphone of the balanced directional type supported by said member, said microphones having sound openings therefor facing in the same direction for the reception of sound, the output of said first microphone varying in response to rotation of said member and being a maximum when said sound openings are substantially aligned with respect to a direction line extending between said member and a source of sound, the output of said second microphone varying in response to rotation of said member and being a minimum when said sound openings are substantially aligned with respect to said direction line, whereby the angular position or direction of said source of sound with respect to said member is established when the outputs of said first and second microphones are respectively maximum and minimum, and means responsive jointly to maximum and minimum outputs of said first and second microphones respectively for producing a signal.

4. A sound direction finder comprising a housing including upper and'lower sections secured together in spaced-apart relation and a member arranged between said sections and mounted for rotation, motor means disposed within said housing for rotating said member, a pair of microphones having sound openings therefor facing in the same direction supported by said member and disposed within said housing, said mlcrophones being so constructed and arranged that they respectively produce maximum and minimum points of output when said openings are substantially in alignment with a direction line extending between said member and a source of sound, and electric circuit means controlled by the said maximum and minimum points of output of said microphones for determining the angular position of said member when said sound openings are substantially aligned with respect to said source of sound, thereby to establish the angular position or direction of said source of sound with respect to said member.

5. A sound direction finder comprising a housing including upper and lower sections secured together in spaced-apart relation and a member arranged between said sections and mounted for rotation, motor means disposed within said housing for rotating said member, a pair of microphones having sound openings therefor facing in the same direction supported by said member and disposed within said housing, said microphones being so constructed and arranged that they respectively produce maximum and minimum points of output when said openings are substantially in alignment with a direction line extending between said member and a source of sound, electric circuit means controlled by the said maximum and minimum points of output of said microphones for determining the angular position of said member -when said sound openings are substantially aligned with respect to said source of sound, thereby to establish the angular position or direction of said source of sound with respect to said member, an indicator, and means controlled by said electric circuit means for causing said indicator to indicate the established direction of said source of sound.

6. A sound direction finder comprising a housing including upper and lower sections secured together in spaced-apart relation and a member arranged between said sections and mounted for rotation, motor means disposed within said housing for rotating said member, a scale carried by one of said sections, a lamp carried by said membar and cooperating with said scale, a pair of microphones having sound openings therefor facing in the same direction supported by said member and disposed within said housing, said microphones being so constructed and arranged that they respectively produce maximum and minimum points of output when said openings are substantially in alignment with a direction line extending between said member and a source or sound, electric circuit means controlled by the said maximum and minimum points of output of said microphones for determining the angular position of said member when said sound openings are substantially aligned with respectto said source of sound, thereby to establish the angular position or direction of said source of sound with respect to said member, and means controlled by said electric circuit means for causing said lamp to illuminate the portion of said scale corresponding to the established direction of said source of sound.

7. A sound direction finder comprising-a housing including upper and lower sections secured together in spaced-apart relation and a member arranged between said sections and mounted for rotation, motor means disposed within said housing for rotating said member, a pair of microphones having sound openings therefor facing in the same direction supported by said member and disposed within said housing, said microphones being so constructed and arranged that they respectively produce maximum and minimum points of output when said openings are substantially in alignment with a direction line extending between said member and a source of sound, electric circuit means controlled by the said maximum and minimum points of output of said microphones for determining the angular position of said member when said sound openings are substantially aligned with respect to said source of sound, thereby to establish the angular position or direction of said source of sound with respect to said member, an indicator including a scale and a rotatable element, a lamp carried by said element and cooperating with said scale, means for rotating said element in accordance with the rotation of said member, and means controlled by said electric circuit means for causing said lamp to illuminate the portion of said scale corresponding to the established direction of said source of sound.

8. A sound direction finder comprising a tubular column, a head carried by the upper end of said column, a housing carried by the lower end of said column and mounted for relative rotation with respect thereto, a member disposed within said head and mounted for relative rotation with respect thereto, a motor disposed within said housing. a transmission connection extending through said column between said motor and said member, whereby said member may be rotated relative to said housing, a pair of microphones supported by said member and disposed within said head and communicating with the exterior through sound openings, said microphones being so constructed and arranged that they respectively produce maximum and minimum points of output when said openings are substantially in alignment with a direction line extending between said member and a source of sound, electric circuit means controlled by the said maximum and minimum points of output of said microphones for determining the angular position of said member when said sound openings are substantially aligned with respect to said source of sound, first indicator means for indicating the relative angular position between said member and said housing, and second indicator means for indicating the relative angular position between said housing and said column, whereby the angular position or direction of said source of sound with respect to said column may be established.

9."A sound direction finder comprising a sup- 19 port adapted to be mounted'on the deck of a ship or the like, a tubular column carried by said support and mounted for relative rotary adjustment with respect thereto, said column projecting both above and below said support, a head carried by the upper end of said column, a housing carried by the lower end of said column and mounted for relative rotation with respect thereto. a member disposed within said head and mounted for relative rotation with respect thereto, a motor disposed within said housing, a transmission con-- nection extending through said column between said motor and said member, whereby said member may be rotated relative to said housing, a plurality of microphone means supported by said member and disposed within said head and communicating with the exterior through sound openings, said microphones being so constructed and arranged that they respectively produce maximum and minimum points 01' output when said openings ,are substantially in alignment with a direction line extending between said member and a source of sound, electric circuit means controlled by the said maximum and minimum points of output of said microphone means for determining the angular position of said member when said sound openings are substantially aligned with respect to said source of sound, first indicator means for indicating the relative angular position between said member and said housing, and second indicator means for indicating the relative angular position between said housing and said column, whereby the angular position or direction of said source of sound with respect to said column may be established.

10. A sound direction finder. comprising a tubular support adapted to be mounted on the deck of a ship or the like, a tubular column disposed within said support and mounted thereon for relative rotary adjustment with respect thereto, said column projecting both above and below said support, means for sealing said support to said column against the entrance of moisture, a head carried by the upper end of said column, a housing carried by the lower end of said column and mounted for relative rotation with respect thereto, a member disposed within said head and mounted for relative rotation with respect thereto, a motor disposed within said housing, a transmission connection extending through said column between said motor and said member, whereby said member may be rotated relative to said housing, a plurality of microphone means supported by said member and disposed within said head and communicating with the exterior through sound openings, said microphones being so constructed and arranged that they respectively produce maximum and minimum points of output when said openings are substantially in alignment with a direction line extending between said member and a source of sound, electric circuit means controlled by the said maximum and minimum points of output of said microphone means for determining the angular position of said member when said sound openings are substantially aligned with respect to said source oi sound, first indicator means for indicating the relative angular position between said member and said housing. and second indicator means for indicating the relative angular position between said housing and said column, whereby the angular position or direction of said source of sound with respect to said column may be established.

11. A sound direction finder comprising a. tubular column, a head carried by the upper. end

oi said column, a housing carried by the lower end of said column and mounted for relative rotation with respect thereto, a member disposed within said head and mounted for relative rota- 5 tion with respect thereto. a motor disposed within said housing, a transmission connection extending through said column between said motor and said member, whereby said member may be rotated relative to said housing, a plurality of microphone means supported by said member and disposed within said head and communicating with the exterior through sound openings, said microphones being so constructed and arranged that they respectively produce maximum and minimum points of output when said openings are substantially in alignment with a direction line extending between said member and a source of sound, amplifier means disposed within said housing and controlled by the said maximum and minimum points oi output of said microphone means, electric circuit means controlled by said amplifier means for determining the angular position 01' said member when said sound openings are substantially aligned with respect to said source of sound, first indicator means for indicating the relative angular position between said member and said housing. and second indicator means for indicating the relative angular position between said housing and said column, whereby the angular position or direction of said source of sound with respect to said column may be established.

12. A sound direction finder comprising a tubular column, a head carried b the upper end of said column, a housing carried by the lower end oi! said column and mounted for relative rotation with respect thereto, a member disposed within said head and mounted i'or relative rotation with respect thereto, a motor disposed within said housing, a transmission connection extending throu h said column between said motor and said member, whereby said member may be rotated relative to said housing, a plurality of microphone means'supported by said member and disposed within said head and communicating with the exterior through sound openings, said microphones being so constructed and arranged that they respectively produce maximum and minimum points or output when said openings are substantially in alignment with a direction line extending between said member and a source of sound, a devicecarried by said housing and operative to indicate when said sound openings occupy a position in substantial alignment with respect to said source of sound, electric circuit means controlled by the said maximum and minimum points of output of said microphone means for governing the operation of said device, first indicator means for indicating the relative angular position between said member and said housing, and second indicator means for indicating the relative angular position between said housing and said column, whereby the angular position or direction of said source of sound with respect to said column may be established.

13. A sound direction finder comprising a housing including upper and lower sections secured together in spaced-apart relation and a member arranged between said sections and mounted for rotation, a motor for rotating said member, a 7 first microphone of the directional type having sound openings therefor facing in one direction supported by said member, a second microphone oi! the balanced directional-type having sound openings therefor facing in the same direction 7 as the sound openings of said first microphone 21 supported by said member, the output of said first microphone being maximum when the sound openings therefor are substantially aligned with respect to a direction line extending between said housing and a source of sound, the output of said second microphone being minimum when the sound openings therefor are substantially aligned with respect to said direction line, and means controlled in response to simultaneous maximum and minimum outputs of said respective first and second microphones for determining the angular position of said housing with respect to a source of sound.

14. A sound direction finder comprising a housing including upper and lower sections secured together in spaced-apart relation and a member arranged between said sections and mounted for rotation, a pair of microphones having sound openings therefor facing in the same direction supported by said member and disposed within said housing, the output of one of said microphones varying in response to rotation of said member and being maximum when said sound openings therefor are substantially in alignment with a source of sound, the output of the other of said microphones varying in response to rotation of said memberand being minimum when said sound openings therefor are substantially in alignment with said source of sound, and means controlled jointly by the maximum and minimum outputs of said microphones for locating the direction of said source of sound with respect to said housing. V

15. In a sound direction finder, a member mounted for rotation, a directional microphone supported by said member, a plurality of sound openings extending in the same direction from one surface of the diaphragm of said microphone for rendering said microphone responsive within narrow limits when said sound openings are directed toward a source or sound, a balanced microphone supported by said member, a Diudering said balanced microphone non-responsive within narrow limits when said last-mentioned sound openings are directed toward a source of sound, means for rotating said member, and means controlled jointly by the response of said directional microphone and the non-response of said balanced microphone for indicating that said sound openings therefor are directed toward a source of sound.

GABRIEL M. GIANNINI.

REFERENCES orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,297,972 Mills Oct. 6, 1942 2,128,398 Cannon Aug. 30, 1938 2,309,109 Hathaway Jan. 26, 1943 2,301,744 Olson Nov. 10, 1942 2,267,480 Talcott Dec. 23, 1941 1,836,397 Rieber Dec. 15, 1931 939,349 Taylor Nov. 9, 1909 420,217 Thompson et a1 Jan. 28, 1890 1,149,123 Fuller Aug. 3, 1915 1,481,923 Nash Jan. 29, 1924 1,299,616 Rieber Apr. 8, 1919 2,166,991 Guanella July 25, 1939 2,299,620 Giannini Oct. 20, 1942 2,061,737 Offenhauser Nov. 24, 1936 1,892,645 Olson et al. Dec. 27, 1932 2,184,247 Baumzweiger Dec. 19, 1939 FOREIGN PATENTS 0 Number Country Date 548.334 German Apr. 9. 1932 297,977 German Jan. 19, 1920 22 rality of sound openings extending from opposite surfaces of the diaphragm of said balanced microphone in the same direction as the sound openings for said directional microphone for ren- 

